CA2012771C - Method of bleaching cellulose pulp with ozone - Google Patents
Method of bleaching cellulose pulp with ozoneInfo
- Publication number
- CA2012771C CA2012771C CA002012771A CA2012771A CA2012771C CA 2012771 C CA2012771 C CA 2012771C CA 002012771 A CA002012771 A CA 002012771A CA 2012771 A CA2012771 A CA 2012771A CA 2012771 C CA2012771 C CA 2012771C
- Authority
- CA
- Canada
- Prior art keywords
- gas
- bleaching
- pulp
- ozone
- pump
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 title claims abstract description 81
- 238000000034 method Methods 0.000 title claims abstract description 73
- 238000004061 bleaching Methods 0.000 title claims abstract description 66
- 229920002678 cellulose Polymers 0.000 title claims abstract description 6
- 239000001913 cellulose Substances 0.000 title claims abstract description 6
- 239000000835 fiber Substances 0.000 claims abstract description 38
- 238000006243 chemical reaction Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000006260 foam Substances 0.000 claims abstract description 16
- 239000000126 substance Substances 0.000 claims abstract description 16
- 239000007844 bleaching agent Substances 0.000 claims abstract description 13
- 238000005086 pumping Methods 0.000 claims abstract 5
- 239000007789 gas Substances 0.000 claims description 79
- 239000000203 mixture Substances 0.000 claims description 17
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 9
- 239000001301 oxygen Substances 0.000 claims description 9
- 229910052760 oxygen Inorganic materials 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 9
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 8
- 239000000460 chlorine Substances 0.000 claims description 8
- 229910052801 chlorine Inorganic materials 0.000 claims description 8
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims description 8
- 238000013019 agitation Methods 0.000 claims description 7
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 6
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 6
- 239000000567 combustion gas Substances 0.000 claims description 6
- 239000004571 lime Substances 0.000 claims description 6
- 238000011084 recovery Methods 0.000 claims description 6
- 239000010802 sludge Substances 0.000 claims description 6
- 239000004155 Chlorine dioxide Substances 0.000 claims description 4
- 102000004190 Enzymes Human genes 0.000 claims description 4
- 108090000790 Enzymes Proteins 0.000 claims description 4
- 235000019398 chlorine dioxide Nutrition 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims 3
- 150000002978 peroxides Chemical class 0.000 claims 3
- 239000000725 suspension Substances 0.000 abstract description 19
- 230000007613 environmental effect Effects 0.000 abstract description 3
- 238000011020 pilot scale process Methods 0.000 abstract description 2
- 239000007787 solid Substances 0.000 description 3
- 239000007900 aqueous suspension Substances 0.000 description 2
- 238000009533 lab test Methods 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- -1 peroxid Chemical compound 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 1
- 229920005372 Plexiglas® Polymers 0.000 description 1
- 229920002522 Wood fibre Polymers 0.000 description 1
- OGIIWTRTOXDWEH-UHFFFAOYSA-N [O].[O-][O+]=O Chemical compound [O].[O-][O+]=O OGIIWTRTOXDWEH-UHFFFAOYSA-N 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000000344 soap Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000002025 wood fiber Substances 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
- D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone
Abstract
Ozone bleaching has been extensively studied in laboratory and pilot scale. It has been proved that at low consistencies, i.e. less than 5 %, ozone dissolves well in water and thus good transfer of substance between the ozone and the fibers in the water is achieved. On the other hand, it has been discovered that the ozone, being a gaseous substance, reacts well also directly with a fiber surface which, however, presupposes that the consistency of the suspension is over 25 %. Further, it has been discovered that in the intermediate range between said consistencies ozone cannot satisfactorily contact the fibers. However, both environmental and pumping factors determine the operation to be carried out at that particular intermediate consistency range of 5 to 25 %.
A characteristic feature of the method of the present invention, which avoids the disadvantages of prior art methods and permits operation at the consistency range of 5 to 25 %, is that cellulose pulp is pumped with a high-consistency pump to a fluidizing mixer in which O2 /O3 gas is introduced and mixed into the pulp so as to generate foam in which the fibers in the pulp and the ozone used as the bleaching agent are brought to contact with each other, and that the pulp is discharged from the mixer to a reaction vessel.
A characteristic feature of the method of the present invention, which avoids the disadvantages of prior art methods and permits operation at the consistency range of 5 to 25 %, is that cellulose pulp is pumped with a high-consistency pump to a fluidizing mixer in which O2 /O3 gas is introduced and mixed into the pulp so as to generate foam in which the fibers in the pulp and the ozone used as the bleaching agent are brought to contact with each other, and that the pulp is discharged from the mixer to a reaction vessel.
Description
~1 2012771 Method of bleaching cellulose pulp with ozone The present invention relates to a method of bleaching cellulose pulp with ozone.
Pulp for the paper and pulp industry must often be bleached in order to produce an end product of adequately high-quality. The most commonly used bleaching agents today are chlorine and oxygen. There is a tendency to avoid the use of chlorine or at least limit it to the minimum because of its damage to the environment. Oxygen is a good bleaching agent but its reaction selectivity is not always adequate whereby also other chemicals must be used. For these reasons, new bleaching agents have been sought. Ozone is one of these.
Ozone bleaching has been extensively studied in laboratory and pilot scale. Ozone has proved to be a good bleaching agent but also expensive and difficult to use as the consistency of the pulp to be bleached has to be very low or very high because of the high reactivity of the ozone. For example, at low consistencies, i.e. below 5 %, ozone is dissolved in the water and thus good transfer of mass between the ozone and the fibers in the water is achieved as the ozone containing water can freely flow between the fibers. It has also been found out that ozone, being a gaseous substance, reacts well directly with a dry fiber surface which presupposes that the consistency is so high, in most cases over 30 %, that there is practically no water on the surface of the fiber or between the fibers. Now the ozone containing gas can freely flow between the fibers.
On the other hand, for pumpability of the suspension, a certain amount of free water in the suspension must be accepted. For environmental and other reasons, it is *
p732/e~
desirable to keep this amount of water as small as possible.
These factors define the range which is optimal for both the apparatus and the environment and lies between 5 and 25 %.
However, ozone cannot contact the fibers in a satisfactory way in this particular consistency range as there is relatively little liquid in the suspension and it is bound in the spaces between the fibers and does not move freely in the suspension, and as ozone, being a gaseous substance, cannot move freely in the suspension because of the state of the suspension.
The problem described above has been solved in the method of the present invention the characterizing features of which are disclosed by the appended patent claims.
The invention provides a method for bleaching pulp with ozone at a consistency range of 5 to 25 %. According to the invention, conditions for good mass transfer are created even if gas or water cannot move freely in the suspension.
The invention is described below in detail with reference to the accompanying drawing figures of which Fig. 1 illustrates a comparison of a state of the art ozone bleaching method and the ozone bleaching method of the present invention;
Fig. 2 illustrates a method according to a preferred embodiment for carrying out the ozone bleaching process of the invention; and Fig. 3 illustrates another preferred embodiment of the ozone bleaching process.
Figure 1 illustrates, as a function of pulp consistency, comparative reaction results of a conventional ozone bleaching process and an ozone bleaching process applying the method of the present invention. In Fig. 1, curve A
;~- p732/e8 ~ ~ j ,., illustrates a typical result from ozone bleaching by a state of the art method. Curve B illustrates the result achieved by ozone bleaching with the method of the invention. By conventional methods at low consistencies (0 to 3 %) ozone dissolves in water and when the pulp-water mixture is agitated, good transfer of substance between the ozone and the fibers is achieved. Thus bleaching is effective in a dilute pulp suspension. At high consistencies (over 25 %) ozone bleaching is carried out mostly as gas phase bleaching. Ozone in gaseous form reacts well with a fiber surface whereby good transfer of substance is gained between the ozone and the fibers. Gas moves freely between the fibers and bleaching proceeds well. At the consistency range of 5 to 25 %, good ozone bleaching requires special measures. The reason of the poor reaction is the somewhat solid nature of the pulp suspension at these consistencies.
Water and air cannot readily move in the half-solid pulp.
As illustrated by Fig. 1, curve B, the same bleaching result as by conventional bleaching is achieved at both low and high consistencies by using the method of the invention.
A characteristic feature of the method of the invention is that in a pulp suspension of the consistency of 5 to 25 %, conditions are created where ozone can contact the fibers.
The simplest way of doing this has proved to be the mixing of ozone gas into the fiber suspension with an intensive high-shear mixer so as to generated foam consisting of wood fibers, water and 2/3 gas. The intense agitation required by the method can be generated by e.g. of known fluidizing mixers produced by A. Ahlstrom Corporation. This mixer typically brings as much mixing efficiency to a small space that fibers or fiber bundles move loose from each other which results in good mixing of chemicals in the fiber suspension. When gas p732/e8 is introduced to this kind of a mixing space, foam is produced.
Table 1 presents the water and gas amounts used when ozone bleaching is performed at the consistency of 10 %. When the consistency is 10 % the pulp suspension contains one ton of fibers and nine tons of water. Approx. two tons of the water is absorbed in the walls of the fibers which leaves about seven tons of free water. The normal ozone dosage is around 1 %, i.e. 10 kg 03. The concentration of the ozone gas is 10 % at the most, in other words the gas mixture contains 10 kg of 03 and 90 kg of 2 gas. As indicated by Table 1, the water/gas ratio varies between 1/10 and 1/1, depending on the pressure, which varies within the range 1 to 10 atm.
Table 1 1 ton fibers 2 tons water in fibers 7 tons free water 7 m3 7 m3 7 m3 1 % 03, 10 kg 03, 90 kg 02 7o m3 14 m3 7 m 3 Pressure 1 bar5 bar 10 bar Water/gas ratio 1/101/2 1/1 The foam generated in a heavy-duty mixer is thus fairly light and the fiber material it contains makes the foam relatively stabile. There is a good transfer of substance between the gas and the fibers in the foam which gives a good bleaching result even though the gas or the water cannot freely move among the fibers.
Laboratory tests with a batch-type fluidizing mixer proved that large amounts of gas could be brought into the pulp suspensions. The tests were performed so that the gas and the pulp suspension were intensively mixed for a short time (approx. 1 second) and then the bleaching reaction was p732/e8 allowed to happen without lntensive mixing. The gas had, however, a tendency to separate, and therefore a better bleaching result in the laboratory batch mixer was achieved whem the gaseous chemicals first were intensively mixed into the fiber suspension in a fluidized state and the resulting gas-water-fiber foam or mixture was lightly agitated in order to prevent separation of gas.
Figure 2 illustrates one possible way of carrying out the ozone bleaching. Pulp 7 is pumped with a high-consistency pump 1 to an intensive mixer 2 into which ozone gas 5 is introduced. From the mixer, the pulp 7 is transferred to a reaction vessel 3 and therefrom to gas separation 4.
After the reaction, residual gas 6, which is mainly the oxygen added to the pulp with the ozone 5, must be separated from the pulp. From the gas separation 4 the pulp flows on to further treatment. It is sometimes necessAry to arrange light agitation in the reaction vessel 3 to prevent the foam or mixture formed in the mixer 2 from collapsing.
The agitation can be accomplished by an agitator or by arranging proper flow conditions in the vessel 3.
Figure 3 illustrates an alternative ozone bleach~ng flow sheet with several ozone feed stages. The amount of the ozone to be introduced to the process may be so large that it is not advantageous to add all the gas at the same time. Then the method illustrated in Fig. 3 may be employed. Pulp 18 is pumped with a high-consistency pump 11 (preferably a fluidizing centrifugal pump by A. Ahlstrom Corporation) to a mixer 12 into which ozone 19 is introduced. Pulp 18 flows via reaction vessel 13 to a gas-removing high-consistency pump 14 (preferably a fluidizing, gas-separating centrifugal pump by A. Ahlstrom Corporation). Residual gas 21 is removed. From the high-consistency pump 14 the pulp flows to a second mixer 15,into which ozone 20 is introduced. After reaction 16 and p732/e8 _~ 6 gas removal 17 the pulp flows on for a further treatment stage. Again the reaction vessels 13 and 14 may be equipped with some kind of agitaion.
It is clear that more than two bleaching stages can be carried out in the corresponding way. The stages can be pressurized, pressureless or performed at underpressure.
The density of the produced foam can be regulated by choosing a desired pressure.
Pilot tests were performed according to a flow sheet corresponding to figure 2. Due to practical reasons it was not possible to use ozone gas but normal air. The goal of the tests was to study mixing of large amounts of gas into fiber suspensions. The reaction vessel 3 was partly replaced by a plexiglass pipe where the formed foam or mixture could be inspected. The foam or mixture varied much according to the surface tension of the water suspension, the type of fiber, and the amount of gas. In some tests the foam or mixture looked much like a snowstorm where bundles of fibres flew in a gas like snow flakes in air but in the gas there also flew water drops and free single fibers. It is clear that high mixing intensity is needed to form a foam or mixture like this from the original somewhat solid fiber suspension of the consistency of about 10 %. It is also clear that some light agitation or special fluid conditions are nee~e~ to prevent the foam or mixture from collapsing. Other tests with soap added to reduce surface tension produced more milk-like foams.
The residual gas 6, 21, 22 produced by the reaction can be used in many ways. The typical ozone gas contains 9 parts oxygen per each part ozone. The residual gas is thus mainly oxygen as oxygen, because of its lower reactivity, does not have enough time to react. The residual oxygen gas can be used in any other stage of the p732/e8 I
pulp production process, for example as additional chemical elsewhere in the ble~ch~ng plant or as combustion gas e.g.
in a soda recovery boiler or in a lime sludge reburning kiln.
Example 1 In a laboratory test, pulp was bleached with the sequence OZDED instead of the conventional OCEDED (O s oxygen, Z =
ozone, E = alkaline extraction, D = clorine dioxide). All bleaching stages were performed at the consistency of 10%.
The goal was to verify that Z can replace CE and that the Z stage can be performed at the consistency of 10 %.
With an ozone dosage of about 0.9 %, the kappa number after the oxygen stage could be reduced to 8 - 9 in ozone stage without damaging the fibers. With a conventional CE
stage, the kappa number is reduced to about 5 - 6 or somewhat lower than in the Z stage. However, the reduction in the Z stage is big enough to enable final bleaching with DED. It is thus possible to completely replace the chlorine with ozone by using medium consistency (10 %) ozone bleaching. This is a significant improvement as the severe environmental problems connected with chlorine are thus avoided.
The ozone stage performed at the consistency of 10 % was also compared with ozone stages performed at the consistencies of 1 % and 30 %. It turned out that ozone bleaching performed at the consistencies of 1 % and 10 %
gave approximately the same result. This is probably due to good mass transfer in a very dilute agitated solution and in a foam-type mixture. The bleaching performed at the consistency of 30 % gave somewhat worse results. This is probably due to the fact that in a pulp of the consistency of 30 %, there are always fairly big flakes of fibers into the inside of which the ozone cannot reach properly, with p732/e8 the result that the surface of the flakes becomes overbleached and the inside unble~ched.
Example 2 A mill feasibility study was performed to evaluate the size of the machinery neeAe~ for ozone bleaching at the consistencies of 1 %, 10 %, and 30 %.
At 1 %, a reaction vessel provided with agitation and operating at 1 % fiber-water suspension was neeAeA into which oxygen-ozone gas was added. A residual gas collecting system was nePAPA as well as a filter machine which after the bleaching raised the consistency to 10 - 15 % before the next process step.
At 10 %, only one mixer with high shearing capacity was nePAeA, and a small reaction vessel with light agitation created by an agitator or flow conditions. No filter was needed but only a small gas separator before the next process step.
At 30 %, a press was neeAe~ before the reaction tower to raise the consistency. Additionally, a high-consistency mixer was neeAPA, and a reaction tower capable of handling solid-gas reactions and provided with some type of intermediate bottoms. After the reaction tower, a dilution, gas separation and discharge system was nePAed.
It was obvious that the machinery needed for bleaching at the consistency of 10 % was by far the cheapest and simplest.
As can be comprehended from the above description, a new method avoiding the disadvantages of the prior art ozone bleaching methods has been developed. Only two preferred applications of the method have been described above which p732/e8 g in no way intend to limit the invention from what has been presented in the appended patent claims which alone define the scope of protection and coverage of the invention. Thus, although only a few bleaching agents have been mentioned in the above examples, also the other bleaching stages may use any conce1vable bleaching agent, e.g. chlorine, ozone, peroxid, chlorine dioxide, sodium hydroxide or enzymes.
p732/e8
Pulp for the paper and pulp industry must often be bleached in order to produce an end product of adequately high-quality. The most commonly used bleaching agents today are chlorine and oxygen. There is a tendency to avoid the use of chlorine or at least limit it to the minimum because of its damage to the environment. Oxygen is a good bleaching agent but its reaction selectivity is not always adequate whereby also other chemicals must be used. For these reasons, new bleaching agents have been sought. Ozone is one of these.
Ozone bleaching has been extensively studied in laboratory and pilot scale. Ozone has proved to be a good bleaching agent but also expensive and difficult to use as the consistency of the pulp to be bleached has to be very low or very high because of the high reactivity of the ozone. For example, at low consistencies, i.e. below 5 %, ozone is dissolved in the water and thus good transfer of mass between the ozone and the fibers in the water is achieved as the ozone containing water can freely flow between the fibers. It has also been found out that ozone, being a gaseous substance, reacts well directly with a dry fiber surface which presupposes that the consistency is so high, in most cases over 30 %, that there is practically no water on the surface of the fiber or between the fibers. Now the ozone containing gas can freely flow between the fibers.
On the other hand, for pumpability of the suspension, a certain amount of free water in the suspension must be accepted. For environmental and other reasons, it is *
p732/e~
desirable to keep this amount of water as small as possible.
These factors define the range which is optimal for both the apparatus and the environment and lies between 5 and 25 %.
However, ozone cannot contact the fibers in a satisfactory way in this particular consistency range as there is relatively little liquid in the suspension and it is bound in the spaces between the fibers and does not move freely in the suspension, and as ozone, being a gaseous substance, cannot move freely in the suspension because of the state of the suspension.
The problem described above has been solved in the method of the present invention the characterizing features of which are disclosed by the appended patent claims.
The invention provides a method for bleaching pulp with ozone at a consistency range of 5 to 25 %. According to the invention, conditions for good mass transfer are created even if gas or water cannot move freely in the suspension.
The invention is described below in detail with reference to the accompanying drawing figures of which Fig. 1 illustrates a comparison of a state of the art ozone bleaching method and the ozone bleaching method of the present invention;
Fig. 2 illustrates a method according to a preferred embodiment for carrying out the ozone bleaching process of the invention; and Fig. 3 illustrates another preferred embodiment of the ozone bleaching process.
Figure 1 illustrates, as a function of pulp consistency, comparative reaction results of a conventional ozone bleaching process and an ozone bleaching process applying the method of the present invention. In Fig. 1, curve A
;~- p732/e8 ~ ~ j ,., illustrates a typical result from ozone bleaching by a state of the art method. Curve B illustrates the result achieved by ozone bleaching with the method of the invention. By conventional methods at low consistencies (0 to 3 %) ozone dissolves in water and when the pulp-water mixture is agitated, good transfer of substance between the ozone and the fibers is achieved. Thus bleaching is effective in a dilute pulp suspension. At high consistencies (over 25 %) ozone bleaching is carried out mostly as gas phase bleaching. Ozone in gaseous form reacts well with a fiber surface whereby good transfer of substance is gained between the ozone and the fibers. Gas moves freely between the fibers and bleaching proceeds well. At the consistency range of 5 to 25 %, good ozone bleaching requires special measures. The reason of the poor reaction is the somewhat solid nature of the pulp suspension at these consistencies.
Water and air cannot readily move in the half-solid pulp.
As illustrated by Fig. 1, curve B, the same bleaching result as by conventional bleaching is achieved at both low and high consistencies by using the method of the invention.
A characteristic feature of the method of the invention is that in a pulp suspension of the consistency of 5 to 25 %, conditions are created where ozone can contact the fibers.
The simplest way of doing this has proved to be the mixing of ozone gas into the fiber suspension with an intensive high-shear mixer so as to generated foam consisting of wood fibers, water and 2/3 gas. The intense agitation required by the method can be generated by e.g. of known fluidizing mixers produced by A. Ahlstrom Corporation. This mixer typically brings as much mixing efficiency to a small space that fibers or fiber bundles move loose from each other which results in good mixing of chemicals in the fiber suspension. When gas p732/e8 is introduced to this kind of a mixing space, foam is produced.
Table 1 presents the water and gas amounts used when ozone bleaching is performed at the consistency of 10 %. When the consistency is 10 % the pulp suspension contains one ton of fibers and nine tons of water. Approx. two tons of the water is absorbed in the walls of the fibers which leaves about seven tons of free water. The normal ozone dosage is around 1 %, i.e. 10 kg 03. The concentration of the ozone gas is 10 % at the most, in other words the gas mixture contains 10 kg of 03 and 90 kg of 2 gas. As indicated by Table 1, the water/gas ratio varies between 1/10 and 1/1, depending on the pressure, which varies within the range 1 to 10 atm.
Table 1 1 ton fibers 2 tons water in fibers 7 tons free water 7 m3 7 m3 7 m3 1 % 03, 10 kg 03, 90 kg 02 7o m3 14 m3 7 m 3 Pressure 1 bar5 bar 10 bar Water/gas ratio 1/101/2 1/1 The foam generated in a heavy-duty mixer is thus fairly light and the fiber material it contains makes the foam relatively stabile. There is a good transfer of substance between the gas and the fibers in the foam which gives a good bleaching result even though the gas or the water cannot freely move among the fibers.
Laboratory tests with a batch-type fluidizing mixer proved that large amounts of gas could be brought into the pulp suspensions. The tests were performed so that the gas and the pulp suspension were intensively mixed for a short time (approx. 1 second) and then the bleaching reaction was p732/e8 allowed to happen without lntensive mixing. The gas had, however, a tendency to separate, and therefore a better bleaching result in the laboratory batch mixer was achieved whem the gaseous chemicals first were intensively mixed into the fiber suspension in a fluidized state and the resulting gas-water-fiber foam or mixture was lightly agitated in order to prevent separation of gas.
Figure 2 illustrates one possible way of carrying out the ozone bleaching. Pulp 7 is pumped with a high-consistency pump 1 to an intensive mixer 2 into which ozone gas 5 is introduced. From the mixer, the pulp 7 is transferred to a reaction vessel 3 and therefrom to gas separation 4.
After the reaction, residual gas 6, which is mainly the oxygen added to the pulp with the ozone 5, must be separated from the pulp. From the gas separation 4 the pulp flows on to further treatment. It is sometimes necessAry to arrange light agitation in the reaction vessel 3 to prevent the foam or mixture formed in the mixer 2 from collapsing.
The agitation can be accomplished by an agitator or by arranging proper flow conditions in the vessel 3.
Figure 3 illustrates an alternative ozone bleach~ng flow sheet with several ozone feed stages. The amount of the ozone to be introduced to the process may be so large that it is not advantageous to add all the gas at the same time. Then the method illustrated in Fig. 3 may be employed. Pulp 18 is pumped with a high-consistency pump 11 (preferably a fluidizing centrifugal pump by A. Ahlstrom Corporation) to a mixer 12 into which ozone 19 is introduced. Pulp 18 flows via reaction vessel 13 to a gas-removing high-consistency pump 14 (preferably a fluidizing, gas-separating centrifugal pump by A. Ahlstrom Corporation). Residual gas 21 is removed. From the high-consistency pump 14 the pulp flows to a second mixer 15,into which ozone 20 is introduced. After reaction 16 and p732/e8 _~ 6 gas removal 17 the pulp flows on for a further treatment stage. Again the reaction vessels 13 and 14 may be equipped with some kind of agitaion.
It is clear that more than two bleaching stages can be carried out in the corresponding way. The stages can be pressurized, pressureless or performed at underpressure.
The density of the produced foam can be regulated by choosing a desired pressure.
Pilot tests were performed according to a flow sheet corresponding to figure 2. Due to practical reasons it was not possible to use ozone gas but normal air. The goal of the tests was to study mixing of large amounts of gas into fiber suspensions. The reaction vessel 3 was partly replaced by a plexiglass pipe where the formed foam or mixture could be inspected. The foam or mixture varied much according to the surface tension of the water suspension, the type of fiber, and the amount of gas. In some tests the foam or mixture looked much like a snowstorm where bundles of fibres flew in a gas like snow flakes in air but in the gas there also flew water drops and free single fibers. It is clear that high mixing intensity is needed to form a foam or mixture like this from the original somewhat solid fiber suspension of the consistency of about 10 %. It is also clear that some light agitation or special fluid conditions are nee~e~ to prevent the foam or mixture from collapsing. Other tests with soap added to reduce surface tension produced more milk-like foams.
The residual gas 6, 21, 22 produced by the reaction can be used in many ways. The typical ozone gas contains 9 parts oxygen per each part ozone. The residual gas is thus mainly oxygen as oxygen, because of its lower reactivity, does not have enough time to react. The residual oxygen gas can be used in any other stage of the p732/e8 I
pulp production process, for example as additional chemical elsewhere in the ble~ch~ng plant or as combustion gas e.g.
in a soda recovery boiler or in a lime sludge reburning kiln.
Example 1 In a laboratory test, pulp was bleached with the sequence OZDED instead of the conventional OCEDED (O s oxygen, Z =
ozone, E = alkaline extraction, D = clorine dioxide). All bleaching stages were performed at the consistency of 10%.
The goal was to verify that Z can replace CE and that the Z stage can be performed at the consistency of 10 %.
With an ozone dosage of about 0.9 %, the kappa number after the oxygen stage could be reduced to 8 - 9 in ozone stage without damaging the fibers. With a conventional CE
stage, the kappa number is reduced to about 5 - 6 or somewhat lower than in the Z stage. However, the reduction in the Z stage is big enough to enable final bleaching with DED. It is thus possible to completely replace the chlorine with ozone by using medium consistency (10 %) ozone bleaching. This is a significant improvement as the severe environmental problems connected with chlorine are thus avoided.
The ozone stage performed at the consistency of 10 % was also compared with ozone stages performed at the consistencies of 1 % and 30 %. It turned out that ozone bleaching performed at the consistencies of 1 % and 10 %
gave approximately the same result. This is probably due to good mass transfer in a very dilute agitated solution and in a foam-type mixture. The bleaching performed at the consistency of 30 % gave somewhat worse results. This is probably due to the fact that in a pulp of the consistency of 30 %, there are always fairly big flakes of fibers into the inside of which the ozone cannot reach properly, with p732/e8 the result that the surface of the flakes becomes overbleached and the inside unble~ched.
Example 2 A mill feasibility study was performed to evaluate the size of the machinery neeAe~ for ozone bleaching at the consistencies of 1 %, 10 %, and 30 %.
At 1 %, a reaction vessel provided with agitation and operating at 1 % fiber-water suspension was neeAeA into which oxygen-ozone gas was added. A residual gas collecting system was nePAPA as well as a filter machine which after the bleaching raised the consistency to 10 - 15 % before the next process step.
At 10 %, only one mixer with high shearing capacity was nePAeA, and a small reaction vessel with light agitation created by an agitator or flow conditions. No filter was needed but only a small gas separator before the next process step.
At 30 %, a press was neeAe~ before the reaction tower to raise the consistency. Additionally, a high-consistency mixer was neeAPA, and a reaction tower capable of handling solid-gas reactions and provided with some type of intermediate bottoms. After the reaction tower, a dilution, gas separation and discharge system was nePAed.
It was obvious that the machinery needed for bleaching at the consistency of 10 % was by far the cheapest and simplest.
As can be comprehended from the above description, a new method avoiding the disadvantages of the prior art ozone bleaching methods has been developed. Only two preferred applications of the method have been described above which p732/e8 g in no way intend to limit the invention from what has been presented in the appended patent claims which alone define the scope of protection and coverage of the invention. Thus, although only a few bleaching agents have been mentioned in the above examples, also the other bleaching stages may use any conce1vable bleaching agent, e.g. chlorine, ozone, peroxid, chlorine dioxide, sodium hydroxide or enzymes.
p732/e8
Claims (38)
1. A method of bleaching cellulose pulp with ozone, characterized in that the pulp is bleached in the form of a foam-like mixture at the consistency range of 5 to 25 %.
2. A method as claimed in claim 1, characterized in - pumping the pulp with a medium consistency pump to a fluidizing mixer, - feeding O2 / O3 gas into the pulp therein, - bringing the ozone serving as the bleaching agent in contact with the fibers of the pulp by means of mixing said gas into the pulp, and - discharging the pulp from the mixer into a reaction vessel.
3. A method as claimed in claim 2, characterized in - performing the bleaching in at least two steps such that - residual gas is removed after the previous step in a reaction vessel, and - additional O2/O3 gas is added in the mixer prior to the later step.
4. A method as claimed in claim 1, characterized in that the foam is a mixture of water, fibers, and O2/O3 gas.
5. A method as claimed in claim 1, characterized in - mixing the O2/O3 gas into the pulp by a fluidizing mixer, whereby the foam-like mixture required by the bleaching reactions is produced.
6. A method as claimed in claim 2, characterized in - separating the residual gas from the pulp after at least one bleaching stage.
7. A method as claimed in claim 3, characterized in - separating the residual gas by a gas-removing pump used for pumping the pulp for further treatment.
8. A method as claimed in claim 7, characterized in that the head produced by the second pump is low or negligible and the pump is used mainly for gas separation and the actual flow is kept up by a previuos pump.
9. A method as claimed in claim 3 or 6, characterized in that the residual gas is fed to another stage of the process, e.g. to serve as additional chemical in the bleaching plant or as combustion gas in a soda recovery boiler or a lime sludge reburning kiln.
10. A method as claimed in claim 7, characterized in - introducing the pulp to another mixer after separating the gas therefrom, - feeding O2/O3 gas into the pulp in said mixer, - mixing said gas with the pulp so as to produce a mixture permitting the bleaching reaction between the ozone and the fibers, and - discharging the pulp into a reaction vessel.
11. A method as claimed in claim 1 or 10, characterized in that the bleaching stages are pressurized, pressureless or performed at underpressure.
12. A method as claimed in claim 2, characterized in agitating the pulp in a reaction vessel.
13. A method as claimed in claim 2, characterized in that the ozone bleaching stage is part of a larger bleaching plant where also the other bleaching stages are performed at a consistency of 5 to 25 %.
14. A method as claimed in claim 13, characterized in that the other bleaching stages use at least one of the following bleaching agents: chlorine, ozone, peroxide, chlorine dioxide, sodium hydroxide or enzymes.
15. A method of bleaching cellulose pulp with ozone serving as a bleaching agent comprising introducing the pulp having a consistency of 5 to 25% into a fluidizing mixer, introducing a mixture of oxygen and ozone gas into the mixer, mixing said ozone containing gas with the pulp under intense agitation and under a pressure of 1 to 10 bar thereby forming a fluidized mixture, and discharging the mixture into a reaction vessel.
16. The method of claim 15, wherein the mixing of said ozone containing gas with the pulp takes place for approximately 1 second.
17. A method according to claim 15 or 16, wherein the bleaching is performed in at least two steps such that residual gas is removed after the previous step in a reaction vessel, and additional ozone containing gas is added in the further step.
18. The method according to one of claims 15 or 16, wherein the ozone content in said ozone containing gas is 10% by weight.
19. The method of claim 17, wherein the ozone content in said ozone containing gas is 10% by weight.
20. The method according to one of claims 15 or 16, wherein the residual gas is separated from the pulp after the bleaching stage.
21. The method of claim 17, wherein the residual gas is separated from the pulp after the bleaching stage.
22. The method according to claim 20, wherein the residual gas is separated by a gas removing pump used for pumping the pulp for further treatment.
23. The method of claim 21, wherein the residual gas is separated by a gas removing pump used for pumping the pulp for further treatment.
24. The method according to one of claims 15, 16 or 22, wherein the pulp is introduced into the bleaching process by means of a medium consistency pump.
25. The method of claim 17, wherein the pulp is introduced into the bleaching process by means of a medium consistency pump.
26. The method of claim 23, wherein the pulp is introduced into the bleaching process by means of a medium consistency pump.
27. The method according to claim 22, wherein the gas removing pump is mainly used for gas separation and the actual flow is kept up by said medium consistency pump.
28. The method of claim 23, wherein the gas removing pump is mainly used for gas separation and the actual flow is kept up by said medium consistency pump.
29. The method of claim 20, wherein the gas removing pump is mainly used for gas separation and the actual flow is kept up by said medium consistency pump.
30. The method of claim 21, wherein the gas removing pump is mainly used for gas separation and the actual flow is kept up by said medium consistency pump.
31. The method according to claim 20, wherein the residual gas is fed to another stage of the process, preferably to serve as an additional chemical in the bleaching plant or as combustion gas in a soda recovery boiler or a lime sludge burning kiln.
32. The method of claim 21, wherein the residual gas is fed to another stage of the process, preferably to serve as an additional chemical in the bleaching plant or as combustion gas in a soda recovery boiler or a lime sludge burning kiln.
33. The method of claim 22, wherein the residual gas is fed to another stage of the process, preferably to serve as an additional chemical in the bleaching plant or as combustion gas in a soda recovery boiler or a lime sludge burning kiln.
34. The method of claim 23, wherein the residual gas is fed to another stage of the process, preferably to serve as an additional chemical in the bleaching plant or as combustion gas in a soda recovery boiler or a lime sludge burning kiln.
35. The method of one of claims 15, 16, 22, 23, and 27-34, wherein the ozone bleaching forms a bleaching stage which is part of a larger bleaching plant where the other bleaching stages are performed at a consistency of 5 to 25%.
36. The method of claim 35, wherein the bleaching is performed in at least two steps such that residual gas is removed after the previous step in a reaction vessel, and additional ozone containing gas is added in the further step.
37. The method of claim 35, wherein the other bleaching stages use at least one of the following bleaching agents:
chlorine, ozone, peroxide, chlorine dioxide, sodium hydroxide, or enzymes.
chlorine, ozone, peroxide, chlorine dioxide, sodium hydroxide, or enzymes.
38. The method of claim 36, wherein the other bleaching stages use at least one of the following bleaching agents:
chlorine, ozone, peroxide, chlorine dioxide, sodium hydroxide, or enzymes.
chlorine, ozone, peroxide, chlorine dioxide, sodium hydroxide, or enzymes.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI892243A FI89516B (en) | 1989-05-10 | 1989-05-10 | Foerfarande Foer blekning av cellulosamassa med Otson |
FI892243 | 1989-05-10 |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2012771A1 CA2012771A1 (en) | 1990-11-10 |
CA2012771C true CA2012771C (en) | 1996-03-26 |
Family
ID=8528390
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002012771A Expired - Lifetime CA2012771C (en) | 1989-05-10 | 1990-03-22 | Method of bleaching cellulose pulp with ozone |
CA002054727A Abandoned CA2054727A1 (en) | 1989-05-10 | 1990-03-29 | Method of and apparatus for treating pulp |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002054727A Abandoned CA2054727A1 (en) | 1989-05-10 | 1990-03-29 | Method of and apparatus for treating pulp |
Country Status (9)
Country | Link |
---|---|
US (3) | US5266160A (en) |
EP (2) | EP0397308B1 (en) |
JP (2) | JPH0340888A (en) |
AT (1) | ATE111371T1 (en) |
CA (2) | CA2012771C (en) |
DE (2) | DE69028797T2 (en) |
FI (1) | FI89516B (en) |
RU (1) | RU2025547C1 (en) |
WO (1) | WO1990013344A1 (en) |
Families Citing this family (34)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5472572A (en) * | 1990-10-26 | 1995-12-05 | Union Camp Patent Holding, Inc. | Reactor for bleaching high consistency pulp with ozone |
FI89516B (en) * | 1989-05-10 | 1993-06-30 | Ahlstroem Oy | Foerfarande Foer blekning av cellulosamassa med Otson |
AU636173B2 (en) * | 1989-10-30 | 1993-04-22 | Lenzing Aktiengesellschaft | Method for the chlorine-free bleaching of pulps |
SE467260B (en) * | 1989-12-29 | 1992-06-22 | Kamyr Ab | WHITING CELLULOSAMASSA WITH CHLORIDE Dioxide AND OZONE IN ONE AND SAME STEP |
SE467261B (en) * | 1989-12-29 | 1992-06-22 | Kamyr Ab | WHITING CELLULOSAMASSA WITH CHLORIDE Dioxide AND OZONE IN ONE AND SAME STEP |
US5520783A (en) * | 1990-10-26 | 1996-05-28 | Union Camp Patent Holding, Inc. | Apparatus for bleaching high consistency pulp with ozone |
CA2046717A1 (en) * | 1991-02-06 | 1992-08-07 | Beloit Technologies, Inc. | Method and apparatus for treating fibrous materials with a gaseous reagent |
US5411633A (en) * | 1991-04-30 | 1995-05-02 | Kamyr, Inc. | Medium consistency pulp ozone bleaching |
US5411634A (en) * | 1991-04-30 | 1995-05-02 | Kamyr, Inc. | Medium consistency ozone bleaching |
AT395445B (en) * | 1991-05-02 | 1992-12-28 | Voest Alpine Ind Anlagen | METHOD FOR BLEACHING CELLULOSE-CONTAINING MATERIAL |
FI922279A (en) * | 1991-05-24 | 1992-11-25 | Union Camp Patent Holding | TVAOSTEGSREAKTOR FOER BLEKNING AV MASSA |
NO912449L (en) * | 1991-06-24 | 1992-12-28 | Norske Stats Oljeselskap | MOVABLE PLATFORM FOR SEA. |
ZA924351B (en) * | 1991-06-27 | 1993-03-31 | Ahlstroem Oy | Ozone bleaching process |
FI97024C (en) * | 1991-07-15 | 1996-10-10 | Ahlstroem Oy | Method and apparatus for separating gas from a gas-containing material |
US5286479A (en) * | 1991-12-10 | 1994-02-15 | The Dow Chemical Company | Oral compositions for suppressing mouth odors |
AT400154B (en) * | 1991-12-23 | 1995-10-25 | Voest Alpine Ind Anlagen | Process for bleaching cellulosic materials |
US5370498A (en) * | 1992-03-04 | 1994-12-06 | Rational Gmbh | Apparatus for elimination of gas constituents |
FI925558A (en) | 1992-04-22 | 1993-10-23 | Ahlstroem Oy | FOERFARANDE OCH ANORDNING FOER BLEKNING AV MASSA |
WO1993023135A1 (en) * | 1992-05-19 | 1993-11-25 | Pom Technology Oy Ab | Apparatus and process for pumping and separating a mixture of gas and liquid |
CA2078276C (en) * | 1992-09-15 | 2004-05-25 | Derek Hornsey | Recovery of oxygen-rich gas from ozone bleaching processes |
US5364505A (en) * | 1992-12-07 | 1994-11-15 | Kamyr, Inc. | Pressurized ozone pulp delignification reactor and a compressor for supplying ozone to the reactor |
US5387317A (en) * | 1993-01-28 | 1995-02-07 | The Mead Corporation | Oxygen/ozone/peracetic aicd delignification and bleaching of cellulosic pulps |
US6340409B1 (en) * | 1993-04-29 | 2002-01-22 | Lewis Donald Shackford | Method for multistage bleaching using gaseous reagent in the first stage with controlled gas release |
SE500616C2 (en) * | 1993-06-08 | 1994-07-25 | Kvaerner Pulping Tech | Bleaching of chemical pulp with peroxide at overpressure |
FI97332B (en) * | 1993-12-23 | 1996-08-30 | Pom Technology Oy Ab | Apparatus and method for pumping and separating a mixture of gas and liquid |
SE505680C2 (en) * | 1994-11-15 | 1997-09-29 | Kvaerner Pulping Tech | Reactor for treating pulp with gas, comprising a degassing outlet means |
US6579412B2 (en) * | 1998-05-08 | 2003-06-17 | L'air Liquide - Societe' Anonyme A' Directoire Et Conseil De Surveillance Pour L'etude Et L'exploitation Des Procedes Georges Claude | Process for ozone bleaching of low consistency pulp |
JP3017712B2 (en) * | 1998-05-15 | 2000-03-13 | 松下電送システム株式会社 | Internet facsimile |
US6261679B1 (en) | 1998-05-22 | 2001-07-17 | Kimberly-Clark Worldwide, Inc. | Fibrous absorbent material and methods of making the same |
FI981808A (en) * | 1998-08-24 | 2000-02-25 | Crs Reactor Engineering Uk Ltd | Method for bleaching pulp |
FI20031164A (en) * | 2003-07-09 | 2005-01-10 | Sulzer Pumpen Ag | Method and apparatus for pulping |
FI20050733A (en) * | 2005-06-22 | 2006-12-23 | Sulzer Pumpen Ag | Gas separator, its front wall and separator wheels |
AT510538B1 (en) * | 2010-09-27 | 2013-02-15 | Andritz Ag Maschf | CENTRIFUGAL PUMP |
SE538752C2 (en) * | 2014-11-21 | 2016-11-08 | Innventia Ab | Process for the production of a treated pulp, treated pulp, and textile fibres produced from the treated pulp |
Family Cites Families (34)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FI45574C (en) | 1970-05-11 | 1972-07-10 | Kymin Oy Kymmene Ab | Process for bleaching cellulosic materials. |
US4002528A (en) * | 1972-02-18 | 1977-01-11 | Kamyr, Inc. | Apparatus for processing pulp |
US3832276A (en) * | 1973-03-07 | 1974-08-27 | Int Paper Co | Delignification and bleaching of a cellulose pulp slurry with oxygen |
SE390549C (en) * | 1973-12-20 | 1985-10-17 | Ahlstroem Oy | SET TO BLOW CELLULOSIC MATERIAL WITH ACID OR FREE ACID CONTAINING GAS IN ALKALIC ENVIRONMENT |
JPS524643A (en) * | 1975-06-30 | 1977-01-13 | Kubota Ltd | Disposal apparatus for incoming floating substance |
US4119486A (en) * | 1975-08-14 | 1978-10-10 | Westvaco Corporation | Process for bleaching wood pulp with ozone in the presence of a cationic surfactant |
US4080249A (en) * | 1976-06-02 | 1978-03-21 | International Paper Company | Delignification and bleaching of a lignocellulosic pulp slurry with ozone |
CA1090510A (en) * | 1976-06-02 | 1980-12-02 | Arthur W. Kempf | Delignification and bleaching of a lignocellulosic pulp slurry with ozone |
JPS5430902A (en) * | 1977-06-27 | 1979-03-07 | Seisan Kaihatsu Kagaku Kenkyus | Industrial multistage pulp bleaching method |
US4372812A (en) * | 1978-04-07 | 1983-02-08 | International Paper Company | Chlorine free process for bleaching lignocellulosic pulp |
FI62872C (en) * | 1978-06-06 | 1983-03-10 | Ahlstroem Oy | ANORDNING FOER SILNING AV FIBERSUSPENSIONER |
JPS5540710A (en) * | 1978-09-14 | 1980-03-22 | Hitachi Chem Co Ltd | Pressure-sensitive adhesive composition |
US4209359A (en) * | 1978-10-23 | 1980-06-24 | International Paper Company | Process for removing residual oxygen from oxygen-bleached pulp |
JPS5658086A (en) | 1979-10-17 | 1981-05-20 | Kogyo Gijutsuin | Multistage bleaching method of pulps |
SE419603B (en) * | 1979-11-27 | 1981-08-17 | Kamyr Ab | APPLICATION FOR MIXING TREATMENT AGENTS IN SUSPENSIONS |
US4435193A (en) * | 1980-04-07 | 1984-03-06 | Kamyr Ab | Controlling operation of a centrifugal pump |
US4410337A (en) * | 1980-04-07 | 1983-10-18 | A. Ahlstrom Osakeyhtio | Method and an apparatus for separating a gas from a fibre suspension |
US4362536A (en) * | 1981-06-08 | 1982-12-07 | Kamyr, Inc. | Pulp degassing |
WO1983000816A1 (en) | 1981-09-04 | 1983-03-17 | Weyerhaeuser Co | Method and apparatus for mixing pulp with oxygen |
FI73023C (en) * | 1984-07-17 | 1987-08-10 | Ahlstroem Oy | ANORDINATION FOR AVAILABILITY OF FIBERS AND PENSION. |
US4886577A (en) * | 1985-05-03 | 1989-12-12 | Kamyr, Inc. | Method and apparatus for mixing oxygen gas with medium consistency pulp in a pump discharge |
US4826398A (en) * | 1987-07-06 | 1989-05-02 | Kamyr Ab | Medium consistency pump with self-feeding |
FR2620744A1 (en) * | 1987-09-17 | 1989-03-24 | Degremont | PROCESS FOR THE OZONE TREATMENT OF LIGNO-CELLULOSIC MATERIALS, IN PARTICULAR PAPER PULP AND REACTOR FOR THE IMPLEMENTATION OF SAID METHOD |
DE68928632T2 (en) * | 1988-02-26 | 1998-07-30 | Ahlstroem Oy | Process and apparatus for treating pulp |
US4902381A (en) * | 1988-12-09 | 1990-02-20 | Kamyr, Inc. | Method of bleaching pulp with ozone-chlorine mixtures |
FI89516B (en) * | 1989-05-10 | 1993-06-30 | Ahlstroem Oy | Foerfarande Foer blekning av cellulosamassa med Otson |
ES2038097T5 (en) | 1989-06-06 | 2001-05-01 | Eka Chemicals Ab | PROCEDURE FOR WHITENING PAPER PASTES CONTAINING LIGNOCELLULOSE. |
SE466061B (en) | 1990-04-23 | 1991-12-09 | Eka Nobel Ab | Bleaching of chemical pulp by treatment with first a complexing agent and then a peroxide containing substance |
JPH04244972A (en) | 1991-01-31 | 1992-09-01 | Nec Corp | Surface potentiometer |
SE470065C (en) | 1991-04-30 | 1995-10-12 | Eka Nobel Ab | Treatment of chemical pulp with an acid and then a magnesium and calcium compound in chlorine-free bleaching |
ZA924351B (en) | 1991-06-27 | 1993-03-31 | Ahlstroem Oy | Ozone bleaching process |
FI925159A0 (en) | 1992-11-13 | 1992-11-13 | Ahlstroem Oy | FOERFARANDE FOER BLEKNING AV MASSA |
FI93232C (en) | 1993-03-03 | 1995-03-10 | Ahlstroem Oy | Method for bleaching pulp with chlorine-free chemicals |
SE500616C2 (en) | 1993-06-08 | 1994-07-25 | Kvaerner Pulping Tech | Bleaching of chemical pulp with peroxide at overpressure |
-
1989
- 1989-05-10 FI FI892243A patent/FI89516B/en not_active Application Discontinuation
-
1990
- 1990-03-20 DE DE69028797T patent/DE69028797T2/en not_active Revoked
- 1990-03-20 EP EP90302993A patent/EP0397308B1/en not_active Revoked
- 1990-03-22 CA CA002012771A patent/CA2012771C/en not_active Expired - Lifetime
- 1990-03-22 JP JP2073149A patent/JPH0340888A/en active Pending
- 1990-03-22 RU SU904743775A patent/RU2025547C1/en active
- 1990-03-29 CA CA002054727A patent/CA2054727A1/en not_active Abandoned
- 1990-03-29 EP EP90905543A patent/EP0479789B1/en not_active Expired - Lifetime
- 1990-03-29 AT AT90905543T patent/ATE111371T1/en not_active IP Right Cessation
- 1990-03-29 US US07/772,362 patent/US5266160A/en not_active Expired - Fee Related
- 1990-03-29 JP JP2505785A patent/JPH05500241A/en active Pending
- 1990-03-29 DE DE69012563T patent/DE69012563D1/en not_active Expired - Lifetime
- 1990-03-29 WO PCT/FI1990/000085 patent/WO1990013344A1/en active IP Right Grant
-
1995
- 1995-06-05 US US08/462,691 patent/US6579411B1/en not_active Expired - Lifetime
- 1995-06-05 US US08/463,558 patent/US6547923B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
ATE111371T1 (en) | 1994-09-15 |
DE69012563D1 (en) | 1994-10-20 |
DE69028797T2 (en) | 1997-03-06 |
US6579411B1 (en) | 2003-06-17 |
US6547923B1 (en) | 2003-04-15 |
RU2025547C1 (en) | 1994-12-30 |
FI892243A0 (en) | 1989-05-10 |
FI89516B (en) | 1993-06-30 |
EP0479789B1 (en) | 1994-09-14 |
EP0397308A3 (en) | 1991-04-17 |
FI892243A (en) | 1990-11-11 |
US5266160A (en) | 1993-11-30 |
JPH05500241A (en) | 1993-01-21 |
EP0397308A2 (en) | 1990-11-14 |
JPH0340888A (en) | 1991-02-21 |
WO1990013344A1 (en) | 1990-11-15 |
CA2054727A1 (en) | 1990-11-11 |
CA2012771A1 (en) | 1990-11-10 |
EP0479789A1 (en) | 1992-04-15 |
EP0397308B1 (en) | 1996-10-09 |
DE69028797D1 (en) | 1996-11-14 |
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